1. Field of the Invention
The present invention relates generally to tool holders. Particularly, the present invention relates to blade sharpening holders. More particularly, the present invention relates to honing guides and tool grinding rests.
2. Description of the Prior Art
When sharpening a cutting edge on a tool, it was common to use jigs to hold the tool to be sharpened at a predetermined angle to a grind stone. Typically, the grind stones were water cooled. The grinding jigs usually included a roller which supported a plate upon which the tool was secured. The support plate and roller held the tool at a selected angle against the stone surface. As the stone was moved, the cutting edge was ground to the selected angle. The initial setting of the tool in the jig was critical to the success of the operation.
The present use of such guides is now customarily limited to flat bench stones. The skilled artisan, however, differentiates between grinding and honing. Grinding is considered as defining the basic edge and honing as refining the basic edge to the finished sharp edge. In the normal sharpening process, the edge to be sharpened is initially passed over the coarse stone at a selected angle. This process leaves a ragged edge of the desired angle. The bevel is then refined over a stone of finer particles. Since such stones cut more slowly, the work is done on the part of the bevel which intersects with the face of the tool to provide a micro-bevel.
The micro-bevel selected should be a function of the tool material, the material to be cut and the intended use. Ideally, the bevel angle should be no greater than is necessary to prevent the edge from breaking down so that the wedging action of the tool is minimized as the edge enters the material to be cut.
When manually sharpening a tool's cutting edge, the skilled artisan uses a variety of methods including oil stones, water stones, sandpaper, loose grit or paste on glass, etc. Honing stones are typically rectangular shaped. When using an oil stone, typically a small amount of honing oil, which is a lightweight oil, is usually placed on the honing stone. The skilled artisan then pulls or pushes the cutting edge over the honing stone at the desired angle as if the cutting edge were scrapping the surface of the honing stone, i.e. the cutting edge is pushed or pulled over the honing surface in a perpendicular fashion. Several blade holders to facilitate manual sharpening of a cutting edge over a honing surface have been devised.
U.S. Pat. No. 4,733,501 (1988, McLean) discloses a honing guide. The honing guide includes a tool support plate mounted above a surface-engaging roller. The surface engaging roller is mounted eccentrically so that the height of the tool support plate may be varied to provide a range of honing angles without unclamping the tool from the guide.
U.S. Pat. No. 5,472,375 (1995, Pugh) discloses a blade sharpening angle guide. The blade sharpening guide includes an elongated curved block having a longitudinal slot therethrough. The longitudinal slot releasably holds a knife blade with the blade cutting edge extending a distance outside the slot.
U.S. Pat. No. 6,030,281 (2000, Cozzini et al.) discloses a sharpening apparatus. The sharpening apparatus includes a base member on which a sharpening stone is positioned. A slidable blade guide member is slidably connected to the base member and includes a guide surface that is disposed at an angle relative to the upper surface of the sharpening stone and a mounting mechanism for removably mounting a spatula against the guide surface such that the scraping edge of the spatula is in engagement with the sharpening stone. The slidable blade guide member is manually slidable back and forth to sharpen the scraping edge of the spatula. A fixed blade guide member is also attached to the base member. The fixed blade guide member includes a horizontal slot that is adapted to receive the shaft of a grill scraper. The fixed blade guide member is adapted to provide guided back and forth sliding movement of the grill scraper within the slot and engagement with the sharpening member to sharpen the scraping edge of the grill scraper.
The above-described devices require the cutting edge of the tool to move over and against the sharpening/honing stone in a “scraping” motion. In other words, the motion of the cutting edge to the stone surface is similar to the action used with a scraper/tool. The motion of the cutting edge of the cutting tool against the honing stone surface is perpendicular to the longitudinal axis of the cutting edge. A disadvantage of this type of action is that the honing stone surface develops a concave shape with use thus shortening the useful life of the honing stone. Another disadvantage is that the concave surface of the honing stone produces a cutting edge that is inconsistent since the cutting edge angle changes as the cutting edge moves through the concavity in the stone surface. Yet another disadvantage is that only a portion of the honing stone is used since the holder must be on the stone at the beginning of the honing process in order to insure that the cutting edge is positioned correctly relative to the honing surface.
Therefore, what is needed is a sharpening holder for use in manually sharpening a cutting edge that does not cause the development of a concave surface in the honing stone with extended use. What is further needed is a sharpening holder that allows the use of substantially the entire surface area of the honing stone. What is also needed is a sharpening holder that does not use a “scrapping” action of the cutting edge over the honing surface in order to sharpen the cutting edge.